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8/3/2019 4 4g Wireless Systems Org
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4G WIRELESS SYSTEMS
SEMINAR REPORT2010
Done byRISHAV BAKOLIA
10884
Department of Computer Science & Engineering
RIMT-Institute Of Engineering &
Technology
r
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ACKNOWLEDGMENT
I would like to thank everyone who helped to see this seminar t
completion. In particular, I would like to thank my seminar coordinator Mrs
Muneera.C.R for her moral support and guidance to complete my seminar o
time. Also I would like to thank Mr. C. D. Anil Kumar for his invaluable help an
support.
I would like to take this opportunity to thank Prof. Indiradevi, Head of th
Department, Electronics & Communication Engineering for her support an
encouragement.
I express my gratitude to all my friends and classmates for their support an
help in this seminar.
Last, but not the least I wish to express my gratitude to God almighty for h
abundant blessings without which this seminar would not have been successful.
ABSTRACT
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Fourth generation wireless system is a packet switched wireless system with
wide area coverage and high throughput. It is designed to be cost effective and to provide
high spectral efficiency . The 4g wireless uses Orthogonal Frequency Division
Multiplexing (OFDM), Ultra Wide Radio Band (UWB),and Millimeter wireless. Data
rate of 20mbps is employed. Mobile speed will be up to 200km/hr.The high performance
is achieved by the use of long term channel prediction, in both time and frequency,
scheduling among users and smart antennas combined with adaptive modulation and
power control. Frequency band is 2-8 GHz. it gives the ability for world wide roaming to
access cell anywhere.
1. INTRODUCTION
Wireless mobile-communications systems are uniquely
identified by "generation" designations. Introduced in the early 1980s,
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first-generation (1G) systems were marked by analog-frequency
modulation and used primarily for voice communications. Second -
generation (2G) wireless-communications systems, which made their
appearance in the late 1980s, were also used mainly for voice
transmission and reception The wireless system in widespread use
today goes by the name of 2.5Gan "in-between" service that serves
as a stepping stone to 3G. Whereby 2G communications is generally
associated with Global System for Mobile (GSM) service, 2.5G is
usually identified as being "fueled" by General Packet Radio Services
(GPRS) along with GSM.
In 3G systems, making their appearance in late 2002 and
in 2003, are designed for voice and paging services, as well as
interactive-media use such as teleconferencing, Internet access, and
other services. The problem with 3G wireless systems is bandwidth
these systems provide only WAN coverage ranging from 144 kbps (for
vehicle mobility applications) to 2 Mbps (for indoor static
applications). Segue to 4G, the "next dimension" of wireless
communication. The 4g wireless uses Orthogonal Frequency Division
Multiplexing (OFDM), Ultra Wide Radio Band (UWB), and Millimeter
wireless and smart antenna. Data rate of 20mbps is employed. Mobile
speed will be up
to 200km/hr.Frequency band is 2-8 GHz. it gives the ability for worldwide roaming to access cell anywhere.
2. FEATURES:
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Support for interactive multimedia, voice, streaming video, Internet,
and other broadband services
IP based mobile system
High speed, high capacity, and low cost-per-bit
Global access, service portability, and scalable mobile services
Seamless switching, and a variety of Quality of Service-driven
services
Better scheduling and call-admission-control techniques
Ad-hoc and multi-hop networks (the strict delay requirements of
voice make multi-hop network service a difficult problem)
Better spectral efficiency
Seamless network of multiple protocols and air interfaces (since 4G
will be all-IP, look for 4G systems to be compatible with all common
network technologies, including 802.11, WCDMA, Bluetooth, and Hyper
LAN).
An infrastructure to handle pre-existing 3G systems along with
other wireless technologies, some of which are currently under
development.
3. HISTORY:
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The history and evolution of mobile service from
the 1G(first generation) to fourth generation are as follows. The
process began with the designs in the 1970s that have become known
as 1G. The earliest systems were implemented based on analog
technology and the basic cellular structure of mobile communication.
Many fundamental problems were solved by these early systems.
Numerous incompatible analog systems were placed in service around
the world during the 1980s.The 2G (second generation) systems
designed in the 1980s were still used mainly for voice applications but
were based on digital technology, including digital signal processingtechniques. These 2G systems provided circuit-switched data
communication services at a low speed. The competitive rush to
design and implement digital systems led again to a variety of
different and incompatible standards such as GSM (global system
mobile), TDMA (time division multiple access); PDC (personal digital
cellular) and CDMA (code division multiple access).These systems
operate nationwide or internationally and are today's mainstream
systems, although the data rate for users in these system is very
limited. During the 1990s the next, or 3G, mobile system, which
would eliminate previous incompatibilities and become a truly global
system. The 3G system would have higher quality voice channels, as
well as broadband data capabilities, up to 2 Mbps.An interim step is
being taken between 2G and 3G, the 2.5G. It is basically an
enhancement of the two major 2G technologies to provide increased
capacity on the 2G RF (radio frequency) channels and to introduce
higher throughput for data service, up to 384 kbps. A very important
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aspect of 2.5G is that the data channels are optimized for packet data,
which introduces access to the Internet from mobile devices, whether
telephone, PDA (personal digital assistant), or laptop. However, the
demand for higher access speed multimedia communication in today's
society, which greatly depends on computer communication in digital
format, seems unlimited. According to the historical indication of a
generation revolution occurring once a decade, the present appears to
be the right time to begin the research on a 4G mobile communication
system.
4.ABOUT 4G:
This new generation of wireless is intended to
complement and replace the 3G systems, perhaps in 5 to 10 years.
Accessing information anywhere, anytime, with a seamless connection
to a wide range of information and services, and receiving a large
volume of information, data, pictures, video, and so on, are the keys of
the 4G infrastructures. The future 4G infrastructures will consist of a
set of various networks using IP (Internet protocol) as a common
protocol so that users are in control because they will be able to
choose every application and environment. Based on the developing
trends of mobile communication, 4G will have broader bandwidth,
higher data rate, and smoother and quicker handoff and will focus on
ensuring seamless service across a multitude of wireless systems and
networks. The key concept is integrating the 4G capabilities with all of
the existing mobile technologies through advanced technologies.
Application adaptability and being highly dynamic are the main
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features of 4G services of interest to users. These features mean
services can be delivered and be available to the personal preference
of different users and support the users' traffic, air interfaces, radio
environment, and quality of service. Connection with the network
applications can be transferred into various forms and levels correctly
and efficiently. The dominant methods of access to this pool of
information will be the mobile telephone, PDA, and laptop to
seamlessly access the voice communication, high-speed information
services, and entertainment broadcast services. The fourth generation
will encompass all systems from various networks, public to private;operator-driven broadband networks to personal areas; and ad hoc
networks. The 4G systems will interoperate with 2G and 3G systems,
as well as with digital (broadband) broadcasting systems. In addition,
4G systems will be fully IP-based wireless Internet. This all-
encompassing integrated perspective shows the broad range of
systems that the fourth generation intends to integrate, from satellite
broadband to high altitude platform to cellular 3G and 3G systems to
WLL (wireless local loop) and FWA (fixed wireless access) to WLAN
(wireless local area network) and PAN (personal area network),all with
IP as the integrating mechanism. With 4G, a range of new services and
models will be available. These services and models need to be further
examined for their interface with the design of 4G systems.
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5.IMPLEMENTATION USING 4G
The goal of 4G is to replace the current proliferation of
core mobile networks with a single worldwide core network standard,
based on IP for control, video, packet data, and voice. This will provide
uniform video, voice, and data services to the mobile host, based
entirely on IP.
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Fig:1
The objective is to offer seamless multimedia services
to users accessing an all IP-based infrastructure through
heterogeneous access technologies. IP is assumed to act as an
adhesive for providing global connectivity and mobility among
networks.
An all IP-based 4G wireless network has inherent
advantages over its predecessors. It is compatible with, and
independent of the underlying radio access technology. An IP wireless
network replaces the old Signaling System 7 (SS7)
telecommunications protocol, which is considered massively
redundant. This is because SS7 signal transmission consumes a larger
part of network bandwidth even when there is no signaling traffic for
the simple reason that it uses a call setup mechanism to reserve
bandwidth, rather time/frequency slots in the radio waves. IP
networks, on the other hand, are connectionless and use the slots only
when they have data to send. Hence there is optimum usage of the
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available bandwidth. Today, wireless communications are heavily
biased toward voice, even though studies indicate that growth in
wireless data traffic is rising exponentially relative to demand for voice
traffic. Because an all IP core layer is easily scalable, it is ideally suited
to meet this challenge. The goal is a merged data/voice/multimedia
network.
6.TRANSMISSION
Fig:2
An OFDM transmitter accepts data from an IP
network, converting and encoding the data prior to modulation. An IFFT
(inverse fast Fourier transform) transforms the OFDM signal into an IF
analog signal, which is sent to the RF transceiver. The receiver circuit
reconstructs the data by reversing this process. With orthogonal sub-
carriers, the receiver can separate and process each sub-carrier without
IP NETWORK
OFDM
TRANSMITTER
MODULATION
IFFT making
IF analog
RF TRANSMITTER
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interference from other sub-carriers. More impervious to fading and
multi-path delays than other wireless transmission techniques, ODFM
provides better link and communication quality.
7.Wireless Technologies Used In 4G
1. OFDM
2. UWB
3. MILLIMETER WIRELESS4. SMART ANTENNAS
5. LONG TERM POWER PREDICTION
6. SHEDULING AMONG USERS
7. ADAPTIVE MODULATION AND POWER CONTROL
7.1 Orthogonal Frequency Division Multiplexing:
OFDM, a form of multi-carrier modulation, works by
dividing the data stream for transmission at a bandwidth B into N
multiple and parallel bit streams, spaced B/N apart (Figure 3). Each of
the parallel bit streams has a much lower bit rate than the original bit
stream, but their summation can provide very high data rates. N
orthogonal sub-carriers modulate the parallel bit streams, which are
then summed prior to transmission.
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Fig:3
An OFDM transmitter accepts data from an IP network,
converting and encoding the data prior to modulation. An IFFT (inverse
fast Fourier transform) transforms the OFDM signal into an IF analog
signal, which is sent to the RF transceiver. The receiver circuit
reconstructs the data by reversing this process. With orthogonal sub-
carriers, the receiver can separate and process each sub-carrier
without interference from other sub-carriers. More impervious to
fading and multi-path delays than other wireless transmission
techniques, ODFM provides better link and communication quality.
7.1.1Error Correcting:
4G's error-correction will most likely use some type of
concatenated coding and will provide multiple Quality of Service
(QoS) levels. Forward error-correction (FEC) coding adds redundancy
to a transmitted message through encoding prior to transmission.
The advantages of concatenated coding (Viterbi/Reed-Solomon) over
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convolutional coding (Viterbi) are enhanced system performance
through the combining of two or more constituent codes (such as a
Reed-Solomon and a convolutional code) into one concatenated
code. The combination can improve error correction or combine error
correction with error detection (useful, for example, for implementing
an Automatic Repeat Request if an error is found). FEC using
concatenated coding allows a communications system to send larger
block sizes while reducing bit-error rates.
7.2 Ultra Wide Band :
A UWB transmitter spreads its signal over a wide portion
of the RF spectrum, generally 1 GHz wide or more, above 3.1GHz. The
FCC has chosen UWB frequencies to minimize interference to other
commonly used equipment, such as televisions and radios. This
frequency range also puts UWB equipment above the 2.4 GHz range of
microwave ovens and modern cordless phones, but below 802.11a
wireless Ethernet, which operates at 5 GHz.
UWB equipment transmits very narrow RF pulseslow
power and short pulse period means the signal, although of wide
bandwidth, falls below the threshold detection of most RF receivers.
Traditional RF equipment uses an RF carrier to transmit a modulated
signal in the frequency domain, moving the signal from a base band tothe carrier frequency the transmitter uses. UWB is "carrier-free", since
the technology works by modulating a pulse, on the order of tens of
microwatts, resulting in a waveform occupying a very wide frequency
domain. The wide bandwidth of a UWB signal is a two-edged sword.
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The signal is relatively secure against interference and has the
potential for very high-rate wireless broadband access and speed. On
the other hand, the signal also has the potential to interfere with other
wireless transmissions. In addition, the low-power constraints placed
on UWB by the FCC, due to its potential interference with other RF
signals, significantly limits the range of UWB equipment (but still
makes it a viable LAN technology).
One distinct advantage of UWB is its immunity to multi-
path distortion and interference. Multi-path propagation occurs when a
transmitted signal takes different paths when propagating from source
to destination. The various paths are caused by the signal bouncing off
objects between the transmitter and receiverfor example, furniture
and walls in a house, or trees and buildings in an outdoor
environment. One part of the signal may go directly to the receiver
while another; deflected part will encounter delay and take longer to
reach the receiver. Multi-path delay causes the information symbols in
the signal to overlap, confusing the receiverthis is known as inter-
symbol interference (ISI). Because the signal's shape conveys
transmitted information, the receiver will make mistakes when
demodulating the information in the signal. For long-enough delays,
bit errors in the packet will occur since the receiver can't distinguish
the symbols and correctly interpret the corresponding bits.
The short time-span of UWB waveformstypically
hundreds of picoseconds to a few nanosecondsmeans that delays
caused by the transmitted signal bouncing off objects are much longer
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than the width of the original UWB pulse, virtually eliminating ISI from
overlapping signals. This makes UWB technology particularly useful for
intra-structure and mobile communications applications, minimizing
S/N reduction and bit errors.
7.3 Millimeter Wireless:
Using the millimeter-wave band (above 20 GHz) for
wireless service is particularly interesting, due to the availability in this
region of bandwidth resources committed by the governments of some
countries to unlicensed cellular and other wireless applications. Ifdeployed in a 4G system, millimeter wireless would constitute only one
of several frequency bands, with the 5 GHz band most likely dominant.
7.4 Smart Antennas:
A smart antenna system comprises multiple antenna
elements with signal processing to automatically optimize theantennas' radiation (transmitter) and/or reception (receiver) patterns
in response to the signal environment. One smart-antenna variation in
particular, MIMO, shows promise in 4G systems, particularly since the
antenna systems at both transmitter and receiver are usually a
limiting factor when attempting to support increased data rates.
MIMO (Multi-Input Multi-Output) is a smart antenna
system where 'smartness' is considered at both transmitter and the
receiver. MIMO represents space-division multiplexing (SDM)
information signals are multiplexed on spatially separated N
multiple antennas and received on M antennas. Figure 4 shows a
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general block diagram of a MIMO system. Some systems may not
employ the signal-processing block on the transmitter side.
Multiple antennas at both the transmitter and the receiver
provide essentially multiple parallel channels that operate
simultaneously on the same frequency band and at the same time.
This results in high spectral efficiencies in a rich scattering
environment (high multi-path), since you can transmit multiple data
streams or signals over the channel simultaneously. Field experiments
by several organizations have shown that a MIMO system, combined
with adaptive coding and modulation, interference cancellation, and
beam-forming technologies, can boost useful channel capacity by at
least an order of magnitude.
7.5 Long Term Power Prediction:
Fig:4
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Channels to different mobile users will fade
independently. If the channel properties of all users in a cell can be
predicted a number of milliseconds ahead, then it would be possible to
distribute the transmission load among the users in an optimal way
while fulfilling certain specified constraints on throughput and delays.
The channel time-frequency pattern will depend on the scattering
environment and on the velocity of the moving terminal.
In order to take the advantage the channel variability, we
use OFDM system with spacing between subcarrires such that no
interchannel interface occurs for the worst case channel scenario(Low coherence bandwidth).A time-frequency grid constituting of
regions of one time slot and several subcarriers is used such that the
channel is fairly constant over each region. These time-frequency
regions are then allocated to the different users by a scheduling
algorithm according to some criterion.
7.6 Scheduling among Users:
To optimize the system throughput, under specified QoS
requirements and delay constraints, scheduling will be used on
different levels:
7.6.1 Among sectors:-In order to cope with co-channel
interference among neighboring sectors in adjacent cells, time slots
are allocated according to the traffic load in each sector .Information
on the traffic load is exchanged infrequently via an inquiry procedure.
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In this way the interference can be minimized and higher capacity be
obtained.
After an inquiry to adjacent cells, the involved base
stations determine the allocation of slots to be used by each base
station in each sector. The inquiry process can also include
synchronization information to align the transmission of packets at
different base stations to further enhance performance.
7.6.2 Among users:-Based on the time slot
allocation obtained from inquiry process, the user scheduler will
distribute time-frequency regions among the users of each sectorbased on their current channel predictions. Here different degrees of
sophistication can be used to achieve different transmission goals.
7.7 Adaptive modulation and power control:
In a fading environment and for a highly loaded system
there will almost exist users with good channel conditions. Regardlessof the choice of criterion, which could be either maximization of
system throughput or
equalization to user satisfaction, the modulation format for the
scheduled user is selected according to the predicted signal to noise
and interference ratio.
By using sufficiently small time-frequency bins the channel
can be made approximately constant within bins. We can thus use a
flat fading AWGN channel assumption. Furthermore since we have
already determined the time slot allocation, via the inquiry process
among adjacent cells described above we may use an aggressive
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power control scheme, while keeping the interference on an
acceptable level.
For every timeslot, the time-frequency bins in the grid
represent separate channels. For such channels the optimum rate and
power allocation for maximizing the throughput can be calculated
under a total average power constraint. The optimum strategy is to let
one user, the one with best channel, transmit in each of the parallel
channels.
8.ISSUES:
The first issue deals with optimal choice of access
technology, or how to be best connected. Given that a user may be
offered connectivity from more than one technology at any one time,
one has to consider how the terminal and an overlay network choose
the radio access technology suitable for services the user is accessing.
There are several network technologies available today,
which can be viewed as complementary. For example, WLAN is best
suited for high data
rate indoor coverage. GPRS or UMTS, on the other hand, are best
suited for nation wide coverage and can be regarded as wide area
networks, providing a higher degree of mobility. Thus a user of the
mobile terminal or the network needs to make the optimal choice ofradio access technology among all those available. A handover
algorithm should both determine which network to connect to as well
as when to perform a handover between the different networks.
Ideally, the handover algorithm would assure that the best overall
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wireless link is chosen. The network selection strategy should take into
consideration the type of application being run by the user at the time
of handover. This ensures stability as well as optimal bandwidth for
interactive and background services.
The second issue regards the design of a mobility enabled
IP networking architecture, which contains the functionality to deal
with mobility between access technologies. This includes fast,
seamless vertical (between heterogeneous technologies) handovers
(IP micro-mobility), quality of service (QoS), security and accounting.
Real-time applications in the future will require fast/seamlesshandovers for smooth operation.
Mobility in IPv6 is not optimized to take advantage of
specific mechanisms that may be deployed in different administrative
domains. Instead, IPv6 provides mobility in a manner that resembles
only simple portability. To enhance Mobility in IPv6, micro-mobility
protocols (such as Hawaii[5], Cellular IP[6] and Hierarchical Mobile
IPv6[7]) have been developed
for seamless handovers i.e. handovers that result in minimal handover
delay, minimal packet loss, and minimal loss of communication state.
The third issue concerns the adaptation of multimedia
transmission across 4G networks. Indeed multimedia will be a main
service feature of 4G networks, and changing radio access networks
may in particular result in drastic changes in the network condition.
Thus the framework for multimedia transmission must be adaptive. In
cellular networks such as UMTS, users compete for scarce and
expensive bandwidth.
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Variable bit rate services provide a way to ensure service
provisioning at lower costs. In addition the radio environment has
dynamics that renders it difficult to provide a guaranteed network
service. This requires that the services are adaptive and robust
against varying radio conditions.
High variations in the network Quality of Service (QoS)
leads to significant variations of the multimedia quality. The result
could sometimes be unacceptable to the users. Avoiding this requires
choosing an adaptive encoding framework for multimedia
transmission. The network should signal QoS variations to allow theapplication to be aware in real time of the network conditions. User
interactions will help to ensure personalized adaptation of the
multimedia presentation.
9.MOBILITY MANAGEMENT
Features of mobility management in Ipv6:
128-bit address space provides a sufficiently large number of
addresses
High quality support for real-time audio and video transmission,
short/bursty connections of web applications, peer-to-peer applications,
etc.
Faster packet delivery, decreased cost of processing no header
checksum at each relay, fragmentation only at endpoints.
Smooth handoff when the mobile host travels from one subnet to
another, causing a change in its Care-of Address.
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1
10.APPLICATIONS
4G technology is significant because users joining the
network add mobile routers to the network infrastructure. Because
users carry much of the network with them, network capacity and
coverage is dynamically shifted to accommodate changing user
patterns. As people congregate and create pockets of high demand,
they also create additional routes for each other, thus enablingadditional access to network capacity. Users will automatically hop
away from congested routes to less congested routes. This permits the
network to dynamically and automatically self-balance capacity, and
increase network utilization. What may not be obvious is that when
user devices act as routers, these devices are actually part of the
network infrastructure. So instead of carriers subsidizing the cost of
user devices (e.g., handsets, PDAs, of laptop computers), consumers
actually subsidize and help deploy the network for the carrier. With a
cellular infrastructure, users contribute nothing to the network. They
are just consumers competing for resources. But in wireless ad hoc
peer-to-peer networks, users cooperate rather than compete for
network resources. Thus, as the service gains popularity and the
number of users increases, service likewise improves for all users. And
there is also the 80/20 rule. With traditional wireless networks, about
80% of the cost is for site acquisition and installation, and just 20% is
for the technology. Rising land and labor costs means installation costs
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tend to rise over time, subjecting the service providers business
models to some challenging issues in the out years. With wireless
peer-to-peer networking, however, about 80% of the cost is the
technology and only 20% is the installation. Because technology costs
tend to decline over time, a current viable business model should only
become more profitable over time. The devices will get cheaper, and
service providers will reach economies of scale sooner because they
will be able to pass on the infrastructure savings to consumers, which
will further increase the rate of penetration.
10.1 4G Car
With the hype of 3G wireless in the rear view mirror, but the
reality of truly mobile broadband data seemingly too far in the future
to be visible yet on the information super highway, it may seem
premature to offer a test drive 4G. But the good news is, 4G is finally
coming to a showroom near you.
10.2 4G and public safety
There are sweeping changes taking place in transportation
and intelligent highways, generally referred to as Intelligent
Transportation Systems (ITS). ITS is comprised of a number of
technologies, including information processing, communications,
control, and electronics. Using these technologies with our
transportation systems, and allowing first responders access to them,
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will help prevent - or certainly mitigate - future disasters.
Communications, and the cooperation and collaboration it affords, is a
key element of any effective disaster response. Historically, this has
been done with bulky handheld radios that provide only voice to a
team in a common sector. And this architecture is still cellular, with a
singular point of failure, because all transmissions to a given cell must
pass through that one cell. If the cell tower is destroyed in the
disaster, traditional wireless service is eliminated.
4G wireless eliminates this spoke-and-hub weakness of
cellular architectures because the destruction of a single node doesnot disable the network. Instead of a user being dependent on a cell
tower, that user can hop through other users in dynamic, self roaming,
self-healing rings. This is reason enough to make this technology
available to first responders. But there is more: mobility, streaming
audio and video, high-speed Internet, real-time asset awareness, geo-
location, and in-building rescue support. All this , at speeds that rival
cable modems and DSL. Combining 4G with ITS infrastructure makes
both more robust. In 4G architectures, the network improves as the
number of users increases. ITS offers the network lots of users, and
therefore more robustness. Think of every light pole on a highway as a
network element, a user that is acting as a router/repeater for first
responders traveling on those highways. Think of every traffic light as
a network element, ideally situated in the center of intersections with
a 360-degree view of traffic. This is the power of the marriage
between 4G networks and ITS.
10.3 Sensors in public vehicle
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Putting a chemical-biological-nuclear (CBN) warning sensor on
every government-owned vehicle instantly creates a mobile fleet that
is the equivalent of an army of highly trained dogs. As these vehiclesgo about their daily duties of law enforcement, garbage collection,
sewage and water maintenance, etc., municipalities get the added
benefit of early detection of CBN agents. The sensors on the vehicles
can talk to fixed devices mounted on light poles throughout the area,
so positive detection can be reported in real time. And since 4G
networks can include inherent geo-location without GPS, first
responders will know where the vehicle is when it detects a CBN
agent.
10.4 Cameras in traffic light
Some major cities have deployed cameras on traffic lights
and send those images back to a central command center. This is
generally done using fiber, which limits where the cameras can be
hung, i.e., no fiber, no camera. 4G networks allow cities to deploy
cameras and backhaul them wirelessly. And instead of having to
backhaul every camera, cities can backhaul every third or fifth or
tenth camera, using the other cameras as router/repeaters. These
cameras can also serve as fixed infrastructure devices to support the
mobile sensor application described above.
10.5 First responder route selection
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Using fiber to backhaul cameras means that the intelligence
collected flows one way: from the camera to the command center.
Using a 4G network, those images can also be sent from the command
center back out to the streets. Ambulances and fire trucks facing
congestion can query various cameras to choose an alternate route.
Police, stuck in traffic on major thoroughfares, can look ahead and
make a decision as to whether it would be faster to stay on the main
roads or exit to the side roads.
10.6 Traffic control during disasters
4G networks can allow officials to access traffic control boxes
to change inland traffic lanes to green. Instead of having to send
officers to every box on roads being overwhelmed by civilians who are
evacuating, it can all be done remotely, and dynamically.
11.FUTURE
We do have are good reasons for 4G development and a
variety of current and evolving technologies to make 4G a reality.
Highlighting the primary drivers for 4G wireless systems are cost,
speed, flexibility, and universal access. Both service providers and
users want to reduce the cost of wireless systems and the cost of
wireless services. The less expensive the cost of the system, the more
people who will want to own it. The high bandwidth requirements of
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upcoming streaming video necessitates a change in the business
model the service providers usefrom the dedicated channel per user
model to one of a shared-use, as-packets-are-needed model. This will
most likely be the model service providers use when 4G systems are
commonplace (if not before).
Increased speed is a critical requirement for 4G
communications systems. Data-rate increases of 10-50X over 3G
systems will place streaming audio and video access into the hands of
consumers who, with each wireless generation, demand a much richer
set of wireless-system features. Power control will be critical since
some services (such as streaming video) require much more power
than do others (such as voice).
4G's flexibility will allow the integration of several different
LAN and WAN technologies. This will let the user apply one 4G
appliance, most likely a cell-phone/PDA hybrid, for many differenttaskstelephony, Internet access, gaming, real-time information, and
personal networking control, to name a few. A 4G appliance would be
as important in home-networking applications as it would as a device
to communicate with family, friends, and co-workers.
Finally, a 4G wireless phone would give a user the
capability of global roaming and accessthe ability to use a cell phone
anywhere worldwide. At this point, the 4G wireless system would truly
go into a "one size fits all" category, having a feature set that meets
the needs of just about everyone.
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12.CONCLUSION
The mobile technology though reached only at 2.5G now, 4G offers
us to provide with a very efficient and reliable wireless communication
system for seamless roaming over various network including internet
which uses IP network. The 4G system will be implemented in the
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coming years which are a miracle in the field of communication
engineering technology.
13.REFERENCES
1) Communications March 2002 Vol 40 No3
2) Communications October 2002 Vol 38 No 10
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3) Communication Systems :- Simon Haykins
4) www.comsoc.org
5) www.crummer.rollins.edu/journal
6) www.techonline.com
7) www.ieee.org
http://www.comsoc.org/http://www.crummer.rollins.edu/journalhttp://www.techonline.com/http://www.ieee.org/http://www.comsoc.org/http://www.crummer.rollins.edu/journalhttp://www.techonline.com/http://www.ieee.org/